This invention relates to rotor supports in turbo and like machinery, for example air cycle machines. In machines of this general class, a rotor is subjected to dynamic influences and to temperature variations which can create problems in the reliability of its operation and in uniformity of response over long working periods. The rotor is mounted in a bearing cartridge. The establishment of a proper support for the bearing cartridge has been a subject of design experimentation looking toward a maximum damping or absorption of dynamic influences. It has been endeavored to achieve a close machined fit of the cartridge member in its supporting housing but this is impractical in dealing with machine produced parts and mass assembly. Also, a differential response to changing temperature can induce undesirable stresses. It has been suggested to mount the cartridge in a housing with elastomeric interface members, but these offer support characteristics changing with time and temperature, and, moreover, limit environmental conditions in which a rotor assembly can operate.